"I think everyone understands that we've lost two Super Bowls to them so I mean that can give you a little post-traumatic stress when you turn on the tape," coach Kyle Shanahan said. "But I think that's human nature. You've got to make sure you don't get caught up in that. This game has nothing to do with past games. That was last year."

When the Niners and Chiefs kick off Sunday, it will be 252 days since San Francisco saw its Lombardi Trophy dreams slip away repeatedly as Patrick Mahomes and the Chiefs claimed their third championship in four years.

Not much has changed in Kansas City since, but the 49ers enter this matchup with plenty of new faces in important places. They fired defensive coordinator Steve Wilks, replacing him with Nick Sorensen, and hired Brandon Staley to an assistant head coach role to help out.

Injuries have also hit the Niners hard with running back Christian McCaffrey (Achilles tendinitis), defensive tackle Javon Hargrave (torn triceps), linebacker Dre Greenlaw (torn Achilles), safety Talanoa Hufanga (torn ligaments in his wrist), offensive lineman Jon Feliciano (knee) and kicker Jake Moody (right ankle) -- all of whom started in the Super Bowl except for Hufanga -- out of action.

Other Niners, such as defensive linemen Arik Armstead and Chase Young and safety Tashaun Gipson Sr. departed in free agency.

The fact that this game doesn't come with nearly the stakes of the Super Bowl also factors into how the Niners approach this rematch. As tackle Trent Williams put it after last week's win against Seattle: "It's not like we can get payback for losing the Super Bowl. That ship has sailed."

"I mean [it's] probably not as dramatic as I'm sure everybody else is probably thinking," linebacker Fred Warner said. "It's 'Hey, it was what it was.' Moved on. New season, new game, new teams, new players. We're just trying to play up to the best of our ability."

That isn't to say the 49ers wouldn't take a little extra satisfaction in getting a win against the 5-0 Chiefs. Since Shanahan took over in 2017, the Niners are 0-4 against Kansas City, including the two Super Bowl defeats in which the Chiefs overcame double-digit deficits.

Sunday will be the 10th regular-season rematch of the previous year's Super Bowl. The Super Bowl winner has won six of the previous nine, though the Philadelphia Eagles defeated Kansas City in Week 11 last year.

"It's definitely a little emotional, but at this point it's just a game," defensive end Nick Bosa said. "We're just looking at the tape, trying to learn from it. A lot of similarities from last year, a few new guys, but really good defense and offense. They obviously have [Mahomes] back there, so always dangerous."

Making matters more difficult is that Kansas City is fresh coming off a Week 6 bye. The Niners had a "mini bye" after playing last Thursday night but still won't have a rest advantage. For his career, Chiefs coach Andy Reid is 21-4 in the regular season following his team's bye, the best of any head coach (minimum of 10 games) since the bye was instituted in 1990.

Of course, the 3-3 Niners could use a win against any opponent no matter the history and that's the mentality Shanahan wants his team to take this week.

"We're playing a really good AFC opponent," Shanahan said. "We're .500 right now. We want to stay on top of our division and get a win. You think about that stuff going into it but in terms of the way it plays out in the game, it really has no correlation and you try to make sure that it doesn't."